With American forces moving inexorably and almost unopposed towards the complete takeover of Baghdad, with officials of the Iraqi government disappearing, with Saddam Hussein reported to be either dead or in flight, and - most spectacularly - with the city's Shi'ite inhabitants at last furnishing the Anglo-American "liberators" with the enthusiastic greeting, the flowers and rice, they have long awaited, the detested, 35-year-long Baathist tyranny is clearly at its last gasp.
The fall of this bloodiest and most brutal of Arab regimes is a convulsion of potentially enormous consequence, not merely for Iraq itself, but for the whole region in which this rich and potentially prosperous - but now ravaged - country occupies such a pivotal position.
"It presents the United States," said Kenan Makiya, one of the leading thinkers of the Iraqi National Congress, the leading opposition group, "with a historic opportunity that I believe is going to prove as large as anything that happened since the fall of the Ottoman Empire and the entry of the British in 1917."
It is, in fact, back to those times, in a great reversal of history, that the Anglo-American invasion is seen to have taken the Arab world. Iraq is the first of the Arab countries to lose the independence that it only acquired after centuries of foreign rule. The spectacle of Western armies capturing an Arab capital is a profound humiliation, exacerbating the already deep sense of impotence and frustration that afflicts Arab peoples everywhere. It is likened to the loss of Palestine in 1948.
It is all the more shocking in that, as they Arabs see it, the Bush administration, or at least the neo-conservative hawks who dominate it, have an Israeli agenda as much as an American one, in which Iraq is expected to become the fulcrum of a whole new Israel-friendly Arab order.
It is recognised as a defeat not just for Iraq, but for the Arab world, in that Saddam himself is seen to be only the most flagrant embodiment of all that was rotten, despotic and corrupt in the region as a whole.
"Americans and Israelis," said a commentator, "would never have dared to transgress on Arab lands had it not been for the pathetic state of our regimes."
But this self-reproach in no way diminishes the region-wide hatred of the US, now at unprecedented levels. Imagine, then, what the Arabs feel at the spectacle of a large segment of Baghdad's citizens welcoming Americans as liberators.
The great question now is what these "liberators" will do with the country they have liberated. The void which, with his brutality and misrule, Saddam has left behind is so great that Iraq's opposition forces, from within or without, cannot fill it on their own. So will the new masters of Iraq manage to preserve it in one piece, or will it fall into chaos and civil war, and become a prey to the competing interventions of neighbouring states?
That welcome which the long-oppressed and rancorous Shi'ites of Saddam City gave the new occupiers also highlights the principal danger: sectarian strife that could turn very nasty unless it is brought swiftly under control.
For Iraq is by nature one of the most turbulent and fissiparious of Arab countries. It breaks down into three basic ethnic or religious communities: the Sunni Muslims of the centre, who constitute some 15 per cent of the population; the Kurds of the mountainous north, at some 20 per cent; and the Shi'ites of the central and southern plains, at some 65 per cent.
Historically, the Sunnis have always dominated Iraqi political life. Their conception of the kind of country Iraq should be - nationalist and pan-Arab - has shaped its domestic foreign polices since the independence it has now lost. They have always preserved their ascendancy at the price of a centralised authoritarianism and discrimination against the other communities which reached their apogée under Saddam.
So the obverse of that joy in Saddam City is the thirst for revenge against all those - overwhelmingly Sunnis - on which the Saddam regime depended; and, beyond that, an aspiration for a fundamental rearrangement, in the Shi'ites' (and the Kurds') favour, of the confessional balance of power in the whole new order that is about to emerge. The question is whether this can be done in a orderly and peaceful manner, or only in an exceedingly violent one. That depends in great measure on the Americans.
The Americans proclaim the liberation of Iraq as the dawn of a new democratic era. But that will be a challenging undertaking indeed. It is not yet clear what kind of administration they plan to set up, what role in it, in the early stages at least, they will assign to Iraqis themselves.
The US State Department is known to favour a more cautious approach in which only the upper echelons of the existing regime are removed, with the basic administrative structures remaining in place. On the face of it, at least, the Pentagon, where the neo-conservative influences are stronger, is more radical: it professes to want a root-and-branch purge of the existing regime, to be replaced by a fully-democratic federal system, apparently to be presided over by its chosen instrument, Ahmad Chalabi, and his Iraq National Congress.
But it seems already clear that the US plans to establish a degree of direct rule to which, if it lasts for long, most opposition leaders will more and more strenuously object.
This has heightened fears that America's real objectives are less the welfare of the Iraqi people than the promotion of their own strategic and economic interests - and Israel's.
Despite the flowers and rice, there is a great deal of latent anti-American feeling among all Iraqis, and not least the Shi'ites, who have not forgotten the role which the West played in supporting the despot and enabling him to survive for so long. Some are already recalling that, when the British conquered Iraq in 1917, it was the Shi'ite religious leaders and clan chieftains who staged the most effective rebellion against their colonial rule.